Microsoft's top executive for Internet Explorer (IE) today dismissed browser speed trials as "at best, not very useful, and at worst, misleading."

At the same time, Dean Hachamovitch, a vice president who heads the IE team, touted the score of Microsoft's newest IE9 Platform Preview in the well-known SunSpider JavaScript benchmark.

Microsoft's Platform Previews are skeletal editions that lack a user interface, and omit such critical navigational tools as the address bar.

In a lengthy entry on the IE blog, Hachamovitch argued that benchmarks don't realistically reflect the speed of a browser, but instead said what he called "real world scenarios" make a better yardstick.

"We think people should evaluate browser performance with real-world scenarios," said Hachamovitch. "Real-world scenarios involve using all the subsystems in the browser together rather than looking at single subsystems in isolation. Using a narrow slice of features to assess the big picture makes as little sense here as using the Acid tests to understand standards compliance."

Acid3 is the standards benchmark that most browser makers trumpet when they match their software against rivals.

Hachamovitch also called Mozilla's claim that it's building a faster Firefox "odd" because Mozilla reported scores derived from a JavaScript engine "shell," not a complete browser. "Those results don't reflect the user's experience in a browser," said Hachamovitch.

The argument that JavaScript speed doesn't accurately measure browser performance isn't new from Microsoft. During the development of IE8 two years ago, Hachamovitch called the benchmark boasting of competitors like Mozilla and Google a "drag race" that Microsoft wasn't interested in joining.

But Hachamovitch has touted IE9's faster JavaScript speeds, as well as its Acid3 score, in past missives in the eight months since Microsoft began releasing developer-only previews of the new browser.

Last August, for example, he pointed out that IE9 Platform Preview 4 scored better on the SunSpider suite than all rivals except Google's Chrome and Opera Software's Opera.

On one test that Hachamovitch cited as an alternative to SunSpider, IE9 Platform Preview 7 actually took longer to solve 1,000 Sudoku puzzles than Chrome's current beta version on Windows. (However, Microsoft's preview beat Chrome's "dev" build, which is roughly equivalent to IE9's Platform Preview, in the same test.)

"There's more to real world performance than JavaScript," Hachamovitch said.

According to Computerworld's last SunSpider tests, IE9 Beta, which launched in mid-September, lags behind the closest comparable versions of browser from Opera, Mozilla, Google and Apple.

Mozilla and Google did not immediately respond to requests for comment about Microsoft's take on browser performance.